Toroidal lens device



K. D. sMrrH 2,949,819

TOROIDAL LENS DEVICE Aug. 23, 1960 3 Sheets-Sheet 1 Filed sept. 28, 1942 Aug. 23, 1960 K. D. sMxTH TOROIDAL LENS DEVICE 5 Sheets-Sheet 2 Filed Sept. 28, 1942 /N VE N TOR K. o. sM/rf/ ya@ ff/(M iin C@ 2,949,819 Patented Aug. 23, 1960 TOROIDAL LENS DEVICE Kenneth D. Smith, White Plains, N.Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N.Y., a corporation of New York Filed Sept. 28, 1942, Ser. No. 460,013

7 Claims. (Cl. 88-57) This invention relates to optical lenses.

An `object of the invention is to provide an improved form of toroidal lens.

Another object of the invention isv to provide an improved ymounting -for such a lens.

An illustrative arrangement embodying the invention is a photoelectric unit including a photoelectric cell and an `amplilier within a cylindrical stream-lined casing comprising two metallic sections held in position solely through the intermediary of an annular lens which directs light received from any direction around the casing within a given toroidal solid angle to the cathode ot the photoelectric cell within the casing, this unit being adapted to be connected to a projectile through the intermediary of one of said metallic sections.

In an example of practice of the invention a photoelectric cell and vacuum tube amplifier arrangement is housed in a casing `which is adapted to be connected to the head end of a projectile containing an explosive charge. The function of this `unit is to detect the presence of an object such as an airplane in proximity to its path `ot travel due to an impulsive reduction in the amount of light incident on the cell and to cause the explosion of the explosive charge. It no object is encountered the explosive charge is exploded )by other means before lthe projectile approaches near enough to the earth to cause damage by its explosion. In order that the photoelectric cell may receive light from all directions around the projectile transversely to the axis thereof, an annular lens is used to converge light rays on the cathode of the cell which cathode is in the form of the convex surface of a :trustum of a cone. This lens with two generally cylindrical hollow metallic members secured to opposite sides thereof forms a casing `and the lens constitutes the sole mechanical connection Abetween the two mem-bers. One of the members is secured to the head end of the projectile. Output leads from the output of the amplifier arrangement pass through the lens to connectors by means of wlhich this photoelectric unit is connected to the firing mechanism of the projectile. The external surface of this lens is so shaped that light rays from a desired solid angle around the lens are converged on a small annular strip of the inner surface of the lens which strip is slightly raised With respect to the rest of the inner surface to facilitate polishing and the application of an opaque coating on the other portions of the inner surface to shut out light rays outside said desired solid angle. A great advantage of this invention resides in the ease off manufacture of the lens and simplicity of assembly of the unit. The lens itself serves as the guide for the positioning of the photoelectric cell and thus facilitates the 2 assembly very materially. The lens is machined from a ring of clear plastic material and is sufficiently strong to support the part of the casing which is remote from the projectile and which encloses the amplifier and batteries.

Certain divisible subject-matter discloseed in this speciiication is disclosed and claimed in application Serial No. 483,605, led April 19, 1943 for Electro-optical Apparatus.

Other divisible subject-matter disclosed in this speciiication is disclosed `and claimed in Patent 2,885,503, issued May 5, 1959, for Switches Controlled by Forces of Acceleration.

The invention will now be described more in detail having reference to the accompanying drawings.

Fig. 1 is a side view of a photoelectric unit according to this invention partly cut away.

Fig. 2 is a cross section of the annular lens of Fig. 1.

Fig. 3 is a face view of the 'lens of Fig. 2.

Fig. 4 shows the mountingof the lens of Fig. 2 with associated portions ot the casing and photoelectric cell.

Fig. 5 is a schematic drawing of the circuit of a photoelectric unit according to this invention.

Fig. 6 is a side View of a modified form of photoelectric unit according to this invention.

Fig. 7 is a cross section of the annular lens of Fig. 6.

Fig. 8 shows the mounting of the lens of Fig. 7 with associated portions of the casing and photoelectric cell.

Fig. 9 shows another modied form of lens according to this invention with associated portions of the casing and photoelectric cell.

The same reference characters` are used to designate identical elements in the several figures or" the drawing.

As shown in Figs. 1 `and 4, one form or" a photoelectric unit according to this invention comprises an annular lens 5. A hollovs metallic cylinder 6 is secured to the i ight-hand side of lens 5 through the intermediary of an externally threaded tace plate "7. Another hollow metallic cylinder 8 is secured to the left-hand side of lens. 5 by a threaded connection. A streamlined metallic hollo'W member 9 is secured to the cylinder 6 Iby a threaded connection. Lens 5, metallic cylinders 6 and 8 and the metallic member 9 form a container 4 for a photoelectric cell and associated electrical apparatus. The lens 5 is the sole mechanical connection between the metallic portion 8 and the metallic portions 6 and 9 of the casing 4.

Lens 5 is shown in greater detail in Figs. 2 and 3. Lens 5 is in the `form of a toroid cut from a block of transparent plastic material, such as methyl methacrylate, Plexiglas or Lucite H7509. Lens 5 may be injection or compression moulded by the usual processes of shaping this material. The critical dimensions of lens 5 are shown on the drawing. Lens 5 serves two main functions, one of `which is to Agather light at polished surface 10 from within a to-rolidal-shaped solid angle and direct it through a ring-shaped aperture at the polished portion 11 on the inner surface of the lens and the other of which is to mechanically support the two cylindrical portions 6 and 8 of the casing 4 in fixed relative positions. All of the surface of lens 5, except the polished surfaces 10 and 11 and the externally threaded portion 12, is left rough during the machining of the lens by using a linepointed lathe tool for the last cuts and coated with a dull black weatherproof lacquer 13. The thickness of 3 coating 13 is exaggerated in Fig. 2 for purposes of illustration. Three small holes 14, 15 and 16 are drilled through the lens for electrical conductors. Tapped holes 17 `are provided to receive the studs which secure face plate 7 to the lens 5. Lens 5 is drawn very closely to scale in Figs. 2 and 3 so that from the important dimensions shown on the drawing the other dimensions may be readily derived.

The assembly of lens 5, cylinder 8, face plate 7 and photoelectric cell 18 is shown in greater detail in Fig. 4. The face plate 7 is an externally and internally `threaded ring which is held against lens 5 by three rectangular mounting blocks secured by studs which pass through the face plate7 and screw into the tapped holes 17 on the lens 5. Two of these mounting blocks 19 and 20 are shown in Figs. 1 and 4, block 19 being shown in section through a tapped central hole 21 in Fig. 4. The photoelectriccell 18 comprises a glass container having a ring seal 22 and a conical cathode 23 surrounded by an anode (not shown). The photoelectric cell 18 is mounted within the toroidal lens 5 in such a position that the light rays passing through the polished surface 11 or aperture are spread over the cathode surface. The photoelectric cell 18 is held in this position by rubber gaskets 24 and 25 on either side of ring seal 22 Iand externally threaded clamp ring 26 which, when screwed into the internal threads of face plate 7, press the bushing 24 against the right-hand sloping internal surface of -lens 5.

Within the casing portion 8 which is screwed on the externally threaded portion 12 of lens 5, output connectors 27 and 28 are mounted on a structure 29 which is held rigidly against the left-hand face of lens 5 by externally threaded clamp ring 30. The structure 29 comprises a spacing disc 31 and a connector disc 32 held apart by a spacer tube 33. A spacer disc 34 is mounted between the connector disc 32 and the connectors 27 and 28. The elements involved in the mounting of the connectors 27 and 28 also serve to exclude extraneous light from the photoelectric cell 18. The terminals of the photoelectric cell emerge from the right-hand end of the container as viewed in Fig. 4. This end of the cell 18 is sealed with wax by filling the clamping ring slightly overflush. The output lead 35 to outer connector 27 passes through hole 14; the output lead 36 to inner connector 28 passes through hole 16; and the ground lead which is 1connsected to clamp-ing ring 3() passes through hole 15 in ens An amplifier unit 37 which is controlled by photoelecytric cell 18 is secured to the three mounting blocks of which 19 and 20 are shown in Figs. l and 4 within the casing portion 6. The dry batteries which supply the electncal energy for the unit are mounted within the casing portion 9 and electrically connected to the rest of the unit by a suitable multiple contact connector.

The assembled photoelectric unit is secured to the projectile which it is to control by screwing the left end of casmg portion 8 on a suitable externally threaded member provided with contactors corresponding to connectors 27 and 28.

An electrical circuit comprising apparatus suitable for being housed within the container l4 is shown schematically in Fig. 5. This circuit comprises the photoelectric cell 18 coupled to the input stage V1 of a three-stage vacuum tube amplifier 40, a thyratron stage T coupled to the output stage V3 of ampliiier 40 and a load circuit 41 which may be a heater resistance coupled vto the output circuit of the thyratron T. Energizing current is furnished by the battery unit 42 which is housed within the metallic member i9, The battery unit 42 comprises the filament heating battery 43, the plate battery 44, the negative biasing battery 46 and a by-pass condenser 47. The battery 42 is connected to the rest of the circuit by means of a multiple contact connector 48. The filament heating circuit is controlled at contacts 49 of acceleration switch 50. The output circuit of the thyratron T, including the load 41, is controlled at contacts 51 of switch 50. The application of negative blocking potential for the input circuit of the output stage V3 of amplifier 40 is controlled by contacts 52 which may be closed by the forces of acceleration operating on a mass 53 mounted o-n the relatively movable contact of contacts 52.

The input stage V1 of amplifier 40 comprises vacuum tube 54, input resistance 55 and plate resistance 56. The intermediate stage V2 of amplifier 40' comprises vacuum tube 57, input resistance 58 and plate resistance 59. The third or ontput stage V3 of amplifier 40 comp-rises vacuum tube 68, series input resistance 61, shunt input resistances 62 and 63, arming condenser 64, inp-ut condenser 65 and output resistances 66 and 67. The thyratron stage T comprises thyratron tube 68, input biasing resistance 69 yand a self-destruction network 70 which includes a gaseous discharge tube 71, resistance 72 and condenser 73. The amplifier stages V1 and V2 are coupled by condenser 74, stages V2 and V3 by condenser 75 and stages V3 and T by condenser 76. The suppressor grids of tubes 57 and 60 are energized through resistances 77 and 78, respectively, from a portion of battery 44 extending from the grounded terminal 45 to the intermediate connection 79. The suppressor grid `of vacuum tube 54 is connected directly to the intermediate connection 79.

The operation of the circuit of Fig. 5 is briefly as follows:

When the projectile to which the casing 4 is connected is in storage of normal transportation prior to use, the switch 50 is in the condition illustrated in Fig. 5 with contacts 49, 51 and 52 open. A cam 80 pivoted at 82 is held against movement by the spring stop 83. The circuit is deenergized since the filament heating circuit is open at contacts 49 and the output circuit of thyratron stage T is open between the load 41 and the positive terminal of plate battery 44 at contacts 51. When flight of the projectile begins, large forces, due to acceleration, are exerted on the cam 80 which causes it to move in a clockwise direction around the pivot 82 until the projection 86 comes against stop 85. The cam 80 is then held in the new position by the spring stop 83. In this new position contacts 49 and 51 are closed. At lthe same ltime the forces of acceleration acting on mass 53 cause contacts 52 to be closed. Due to the closure of contacts 52 the negative potential of battery 46 is impressed on the grid of vacuum tube 60 through resistances 61 and 62 to block this third amplifier stage V3 and also charges arming condenser 64. Since amplifier stage V3 is blocked the closure of filament heating circuit at contacts 49 and the thyratron output circuit through load circuit 41 at contacts 51 is merely preparatory for further use. When the acceleration drops below a predetermined value contacts 52 are opened as the closing forces of acceleration on mass 53 are reduced. The circuit is brought under the control of the photoelectric cell by being rendered effective or armed gradually as arming condenser 64 discharges at a predetermined rate through resistance 63. This gradual arming of the circuit precludes a premature firing of the projectile due to transients which might be generated by an abrupt arming of the circuit. The circuit is now under the control of the photoelectric cell 18. The circuit constants are so proportioned that a small reduction of light on the cell 18 at a rate represented by the approximate wave front of a 40-cycle sine wave will trigger off the thyr-atron tube. When contacts 51 are closed the charging of condenser 73 through resistance 72 of the self-destruction circuit 70 begins and continues until the charge on condenser 73 reaches a potential Sullicient to break down discharge tube 71. At the time of breakdown a positive potential is impressed on the grid of thyratron tube 68 which is sufficient to trigger oi the thyratron.

From the foregoing brief description it is seen that in operation this photoelectric unit is deenergized during ordinary handling and transportation. During the earlier stages of acceleration the filament and output circuits are energized. The circuit is inelective, however, at this stage due to the blocking potential on the third amplifer stage V3. When the acceleration is reduced the circuit is gradually armed, remaining armed during a predetermined interval before its self-destruction is effected by the breakdown of discharge tube 71.

Another form of photoelectric unit according to this invention will now be described having reference to Figs. 6, 7 and 8. This unit is generally similar to that of Fig. 1. It comprises a casing 90, including a lens 91 which connects one hollow metallic cylinder 6 and another hollow metallic cylinder 92. A streamlined cup-shaped member 9 is secured to cylinder 6. In this embodiment both ends of lens 91 are threaded externally to receive the internally threaded ends of cylinders 9 and 92. The amplier unit 37 is secured to the face of the lens 91 by studs (not shown). The unit 37 carries a photoelectric cell guide 93 which -fts into the central opening of the toroidal lens 91. The cell 18 slides into this guide 93 against a relatively stili spiral spring 94. The cell 18 is held in position against the spring 94 by an insulator block 95. A rubber washer 96 is cemented to the block 95. Block 9S is held between the lens 91 and an internal ridge 97 on cylinder 92. Output connectors 98 and 99 are mounted on block 95. These connectors are in the form of concentric metallic rings each having a plurality of integrally formed compression spring portions. It is thus seen that the lens 91 is the sole means for securing cylinders 6 and 92 in relative position with respect to each other.

The dimensions and relative positions of the refracting surfaces of lens 91 are the same as those of lens 5. All of the surfaces of lens 91, except the external polished surface 100, the internal polished ridge surface 101 and the screw threads, are coated with an opaque dull black weather-proof lacquer 102. The thickness of this coating is greatly exaggerated in the drawing. The lens of Fig. 7 is drawn very closely to scale and therefore shows the relative dimensions of its various portions. Lens 91 will gather light from a given toroidal solid angle, which light is transmitted through the polished surface of ridge 101 to the cathode 23 of photoelectric cell 18.

A modified lens mounting is shown in Fig. 9. Here again photoelectric cell 18 is mounted within an annular lens 110 which forms the sole means of relative support for two metallic portions 111 and 112 of a casing 113 of a photoelectric unit. The portion 111 is threaded internally to `lit the external threads on the right-hand end of lens 110. A support ring 114 has two internally threaded portions 115 and 116. The right-hand portion 115 screws on the external threads of lens 110 and =fts snugly against the lens. The metallic portion 112 fits snugly over the outer ridges of support ring 114 being held in place partly thereby. The ring seal 22 of photoelectric cell 18 is held by an internal lip 117 of support ring 114 through the intermediary of a rubber washer 118. The cell 22 is pressed against the washer 118 by externally threaded ring 119, pressing cell 18 toward the right through the intermediary of rubber ring 120. The lens 110 comprises an external polished surface 121, an internal polished annular slit 122 and a polished conical surface 123 which is totally reflecting for all light rays which enter the surface 121 and after reflection and refraction are converged at the slit 122. In this modification the cell 18 is reversed with respect to the direction in which the lens may be said to look.

What is claimed is:

1. A toroidal lens comprising a toroid of transparent solid material, a complete toric section of the outer periphery of said toroid being polished and having a curvature in a plane containing the axis of the toroid to converge light rays from outside the lens to a focal point located between the said toric section and the axis of said toroid, and an inwardly protruding ridge on the inner periphery of said toroid having a polished toric light transmitting surface located closely adjacent to said focal point and having a width of the order of one-fifteenth the distance of said focal point from said outer toric section.

2. A toroidal lens comprising a toroid of transparent solid material, a complete toric section of the outer periphery of said toroid being polished and having a curvature in a plane containing the axis of the toroid to converge light rays from outside the lens to a focal point located between the said toric section and the axis of sai-d toroid, and a polished ring-shaped light transmitting slit on the inner periphery of said toroid located closely adjacent to said focal point and having a width to form a narrow angular eld of the refracting surface of said toric section.

3.A toroidal lens comprising a toroid of transparent solid material, a complete toric section of the outer periphery of said toroid being polished and having a curvature in a plane containing the axis of the toroid to converge light rays from outside the lens to a focal point located between the said toric section and the axis of said toroid, and a polished ring-shaped light transmitting slit on the inner periphery of said toroid located closely adjacent to said focal point and having a width to form a narrow angular field of the refracting surface of said toric section, said toric section being positioned entirely to one side of a plane perpendicular to the axis of said toroid and intersecting said slit.

4. A toroidal lens comprising a tor-oid of transparent solid material, a complete toric section of the outer periphery of said toroid being polished and having a curvature in a plane containing the axis of the toroid to converge light rays from outside the lens to a focal point located between the said toric section and the axis of said toroid, and an inwardly protruding ridge on the inner periphery of said toroid having a polished toric light transmitting surface located closely adjacent to said focal point and having a width to form a narrow angular field of the reflecting surface of said toric section, said toric section being positioned wholly to one side of a plane perpendicular to the axis of said toroid and intersecting said inwardly protruding ridge.

5. A toroidal lens comprising a toroid of transparent solid material, a complete toric section of the outer periphery of said toroid being polished and having a curva.- ture in a plane containing the axis of the toroid to converge light rays from outside the lens to a focal point located between the said toric section and the axis of said toroid, a conical polished toric section of the surface of said toroid positioned to totally reflect light rays directed -to said focal point to a second focal point located between said toric section and the axis of said toroid, and a polished ring-shaped light transmitting slit on the inner periphery of said toroid located closely adjacent to said second focal point and having a width to form a narrow angular field of the refracting surface of said toric section.

6. A device for highly illuminating a given region adjacent the device, said device comprising a transparent material of a relatively high index of refraction, said device being in the form of a closed loop thus having an outer perimeter and an inner perimeter, a light gathering surface at the outer perimeter shaped to focus the light in the surface of the inner perimeter to thus form a narrow highly illuminated region in the form of a closed loop in the inner surface of the device, whereby the inner region adjacent the device is illuminated.

7. A device for highly illuminating a given region adjacent the device, said device comprising a transparent material of a relatively high index of refraction, said device being in the form of a closed loop thus having an outer perimeter and an inner perimeter, a light gathering surface at the outer perimeter shaped to focus the light in the sur- 7 face ofthe inner perimeter to thus form a narrow highly illuminated region in the form' of a closed loop in the inner surface of the device, whereby the inner region adjacent the deviceis illuminated, said device being provided with opaque matenialexcept at the outer light gathering surface and at the focal region in the inner surface.

References Cited in the le of this patent UNITED .STATES PATENTS 1,085,611 Humbrecht Feb. 3', 1914 1,098,905 Jacob et al June 2, 1914 1,708,027 Ohl Apr. 9, 1929 8 Ives Jan. 12, 1932 Langmuir Y Nov. 21, 1933l Bauersfeld et al.l Ian. 16, 19344` Stanley Iuly16, 1937 Wallace Y Y Nov. 2, 1937 Vos Nov. 22, 1938 Bedford Mar. 21, 1939k Bergmans Jan. 116, 1940 Bitner Dec. 10, 1940 Salmond Apr. 1, 1941 Ferrel Sept. y9, 1941 Kingston Mar. 23, 1943 

